Surface-Sensitive Spectro-electrochemistry Using Ultrafast 2D ATR IR Spectroscopy

Abstract

A new method is presented for the combination of spectro-electrochemistry and femtosecond 2D IR spectroscopy. The key concept is based on ultrathin (similar to nm) conductive layers of noble metals and indium-tin oxide (ITO) as working electrodes on a single-reflection attenuated total reflectance (ATR) element in conjunction with ultrafast, multidimensional ATR spectroscopy. The ATR geometry offers prominent benefits in ultrafast spectro-electrochemistry, that is, surface sensitivity for studying electrochemical processes directly at the solvent-electrode interface as well as the application of strongly IR-absorbing solvents such as water due to a very short effective path length of the evanescent wave at the interface. We present a balanced comparison between usable electrode materials regarding their performance in the ultrafast ATR setup. The electrochemical performance is demonstrated by vibrational Stark-shift spectroscopy of carbon monoxide (CO) adsorbed to platinum-coated, ultrathin ITO electrodes. We furthermore measure vibrational relaxation and spectral diffusion of the stretching mode from surfacebound CO dependent on the applied potential to the working electrode and find a negligible impact of the electrode potential on ultrafast CO dynamics.

Second-order spectral lineshapes from charged interfaces

“…In our analysis of equation (3) for the case of a single-frequency system (n=1), we use ω 1 =2100 cm -1 , which is in the vicinity of nitrile or carbon monoxide systems reported in the literature [15][16][17][18][19] . With an arbitrary value of A 1 M 1 =10, a damping factor, Γ ν , of 15 cm -1 , γ 1 =0 degrees, and !…”

In‐Situ Infrared Spectroscopy Applied to the Study of the Electrocatalytic Reduction of CO2: Theory, Practice and Challenges

“…An exception to the rule above applies for ultrafast electrochemical 2D‐IR ATR‐SEIRAS . In this case the intensity of the signal and avoiding heating of the sample by the intense laser pulse are critical, which implies maximizing the enhancement factor and minimizing absorbance of the IR beam by the metal film.…”

“…[62] An exception to the rule above applies for ultrafast electrochemical 2D-IR ATR-SEIRAS. [122,123] In this case the intensity of the signal and avoiding heating of the sample by the intense laser pulse are critical, which implies maximizing the enhancement factor and minimizing absorbance of the IR beam by the metal film. Films much thinner (0.1-2.5 nm) than those used in conventional ATR-SEIRAS (20-50 nm) are required, despite their high resistance and the possibility of generating abnormal bands.…”

Ultrafast Vibrational Energy Transfer in Catalytic Monolayers at Solid–Liquid Interfaces

“…[24][25][26] Under these circumstances, immobilization of the sample at the interface allows obtaining surface-sensitive signals from solid-liquid interfaces. With this approach, we have recently investigated the ultrafast vibrational dynamics of surface-bound carbon monoxide 17,27 and cyanide 28 as well as self-assembled organic monolayers under various conditions 18,19,29,30 . Figure 1.…”